I burned out the drive clutches on my '94 GMC the other day and am looking for a source for reman transmissions.  I've searched online, but haven't had much luck to far.  I still have first second and reverse, but it won't hold in drive.  It happened while bucking a good wind pulling a trailer with a loader on it.  I haven't crawled underneath to look at it, but I'm pretty sure it's a 4L80.  95,000 miles, I guess it was due.